时间:2019-01-08 作者:英语课 分类:Scientific American(八)月


英语课

You’ve given some thought to oxygen, carbon, uranium. But you’ve probably never mused 1 about the element ytterbium, symbol Yb. A new study by scientists at the National Institute of Standards and Technology, or NIST, says that ytterbium could find a role in super-accurate atomic clocks. The report is in the journal Physical Review Letters.


 


The gold standard, if you will, for atomic clocks, is the element cesium, symbol Cs. Official civilian 2 time is kept by the cesium NIST-F1 fountain clock, accurate to within one second every 100 million years. And the international definition of the second is based on exactly how many vibrations 3 happen when a cesium atom’s electron changes energy levels. How many? 9,192,631,770. Exactly.


 


Anyway, your watch is fine for getting to work about on time, but if you want your GPS to work fine, you need these atomic clocks on Earth and on satellites. And an ytterbium clock has the potential to be even more accurate and stable than the cesium chronometer 4. Wow, I gotta go, look at the time.


 



v.沉思,冥想( muse的过去式和过去分词 );沉思自语说(某事)
  • \"I wonder if I shall ever see them again, \"he mused. “我不知道是否还可以再见到他们,”他沉思自问。 来自《简明英汉词典》
  • \"Where are we going from here?\" mused one of Rutherford's guests. 卢瑟福的一位客人忍不住说道:‘我们这是在干什么?” 来自英汉非文学 - 科学史
adj.平民的,民用的,民众的
  • There is no reliable information about civilian casualties.关于平民的伤亡还没有确凿的信息。
  • He resigned his commission to take up a civilian job.他辞去军职而从事平民工作。
n.摆动( vibration的名词复数 );震动;感受;(偏离平衡位置的)一次性往复振动
  • We could feel the vibrations from the trucks passing outside. 我们可以感到外面卡车经过时的颤动。
  • I am drawn to that girl; I get good vibrations from her. 我被那女孩吸引住了,她使我产生良好的感觉。 来自《简明英汉词典》
n.精密的计时器
  • Murchison followed with his eye the hand of his chronometer.莫奇生的眼睛追随着他的时计的秒针。
  • My watch is more expensive because it's a chronometer.我的手表是精密型的,所以要比你的贵。
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absorbent cloth
Acid Complex Blue GGN
almotriptan
alveolar dead space
analytic aerial triangulation
anaphase in cell division
audio radiation indicator
Banden
baron wilhelm von humboldts
BHIB
bucolone
chesting calender
civil service official
communication between domains
contini
cupferron
cybisterone
De M.
debellator
decorative web
dislodged
doodlebuggers
dyed goods
Eagle's medium
electrophotograph
emission tomography
externally-braced monoplane
federal funds rate
ferroactinolite
fiss
flavicant
fluorosurfactant
goats hair
gydanskiy poluostrov(gydanski pen.)
haldimand
Harang discontinuity
hard shelled egg
healthcorps
Horka
hydrocol naphtha fraction
indigenous alveolar bone
insam
intestinalis arteria
Laval, Pierre
letterly
lie flat
ligamenta costoclaviculare
macro dummy variable of definition
marmylaris buckleyi
Mashileh
mathematics of control
measurement inverter
metal-case magnesite brick
methylene urea
monoclinal folded structure
multi-list processor system
nedy
nonretractile
nonretracting
o-diethylaminotoluene
once-quiet
Onopordum
outhaul winch
peel rubber
peels off
phasings
picture-frames
poor focus
pre-sparking
Rahu
Rayleigh-Jeans formula
reads over
rear ... head
redundant fan
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Rhine Falls
road appreciation
scallopping
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seoc
shifting beam carrier
short-stops
single-screw ship
somatoform
subglossitis diphtheroides
swivelling characteristic
tertiary egg envelope
tire size
topographies
TR cell
tuck ... in
unfruitfully
unlocking lever tube
unvoluntary unemployment
Vailoa
vibrator rectifier
Vinerian
wee willie winkie
zarroli